1. Field of the Invention
The present invention relates to the use of extremely fine-sized aqueous polymeric dispersions, and particularly acrylic-based dispersions having a mean particle size of less than 60 nanometers as textile sizes. More specifically, the invention comprises the use of two or more fine-size aqueous dispersions which when combined together, optimizes the benefits of each dispersion to yield a final product which may be directly applied to natural and synthetic fibers.
2. Technology Description
Heretofore, numerous emulsion latexes have existed. However, the particle sizes of such latexes have generally been large, for example 120 nanometers or larger. Moreover, the use of ultrafine sized latexes as textile sizing agents has not been appreciated.
U.S. Pat. No. 4,177,177 to Vanderhoff et al relates to various methods for making polymeric emulsions which can be utilized to produce latexes. The latexes generally have a particle size greater than 100 nanometers.
U.S. Pat. No. 4,228,047 to Pippin et al relates to an aqueous coating composition comprising a copolymer of at least 95 percent by weight of vinyl acetate and at least 0.1 percent by weight of maleic anhydride which allegedly has been found to have improved starch binder compatibility.
Japanese Disclosure No. 52103588 to Asahi Dow relates to a carpet-backing composition containing 100 parts by weight (as solids content) of a copolymer latex: 200 to 350 parts by weight of inorganic filler and thickener consisting of 30-60 weight percent of a) butadiene: 20-70 weight percent of b) styrene 5-30 weight percent of c) methyl methacrylate: and 1 to 5 weight percent of d) ethylene series of unsaturated carboxylic acid and has an average particle diameter of 60 to 120 nm. By using the latex of small particle diameter for the carpet backing, blistering is prevented.
Belgian Patent No. 812139 to DeSoto, Inc. relates to opaque coatings obtained from a latex comprised of an aqueous suspension of small and large resin particles, the large particles having a Tg less than the small ones and having an average diameter which is greater than twice that of the small particles, the latter forming 20 to 65 weight percent of the total particles. The particles are such that neither the large nor the small ones can, on their own, coalesce when the latex is dried, to form a non-cellular film. The small particles actually give a powder under such conditions. The small particles are preferably polystyrene and the large ones a copolymer of vinyl acetate and an ester of a 4 to 18 carbon atom alkanol and an unsaturated carboxylic acid. The composition contains a minimum amount of solvent and rapidly gives an opaque coating of low porosity upon drying. It may be used for lipstick, crayons, etc.
British Patent No. 1,100,569 to the Dow Chemical Co. relates to acrylic polymer latexes containing large and small particles prepared by 1) heating water containing a soluble catalyst to up to 85.degree. C. in an inert atmosphere, 2) adding 1/3 of a mixture of monomers, 3) carrying on the polymerization for at least 15 minutes, 4) adding an aqueous solution of an anionic emulsifier and an aqueous solution of the polymerization catalyst, and 5) adding the remaining monomer continuously over a period of at least 45 minutes.
U.S. Pat. No. 3,711,435 to DuPont and Co. relates to a stable, aqueous colloidal dispersion prepared by mixing 1) a copolymer of 20 to 80 weight percent ethylene and 80 to 20 weight percent of an aminoalkylacrylate; 2) an acid having a dissociation constant of 10 to 5; and 3) water in proportion to give a solids containing 5 to 30 weight percent and a degree of neutralization of the amino groups of the polymer of at least 40 percent. The mixing is effected at a temperature suitable for dispersing the polymer in particles of size less than 10 nanometers. The resulting dispersions have very small particle sizes so that they may be thinly spread over aluminum substrates to give void free coatings, and as flocculants for removal of suspended matter from water. N,N-dimethylaminoethylmethacrylate is a suitable comonomer.
Japanese Disclosure No. 52-123478 to Kurraray relates to compositions prepared by emulsion polymerization of unsaturated monomers in the presence of a protective colloid which is prepared by cleaving water-solubilized copolymers in the presence of free radicals and by heating. The compound contains units of maleinimide and/or N-substituted maleinimide and units of alpha-olefin as essential components of the main chain.
An article by Ugelstad, El-Aasser, and Vanderhoff, Journal of Polymer Science, Polymer Letters Edition, 11, 503:1973 relates to the production of latex particles by mini-emulsion polymerization of a mixed-emulsifier system including a surfactant and a long-chain alcohol or alkane cosurfactant utilizing ultrasonification.
An article by Atik and Thomas, Journal of American Chemical Society, 103, 4279: 1981 relates to aqueous styrene polymer microemulsions made by bulk polymerization having a number average particle size of from about 20 to about 35 nanometers by utilizing a mixed emulsifier of cetyl-trimethylammonium bromide and hexanol followed by polymerization with an oil soluble azobisisobutyronitrile and irradiation. However, the solids content was very low, less than 2 percent and the amount of emulsifiers utilized was approximately 1.5 times the amount of polymer by weight.
An article by Jayakrishnan and Shah, Journal of Polymer Science, Polymer Letters, 22, 31 984 relates to a bulk polymerization of polystyrene or methyl methacrylate microemulsion particles having a number average size of from about 10 to about 60 nanometers utilizing sodium dihexylsulfosuccinate and ethylene oxide-propylene oxide block copolymers as mixed-emulsifiers and an oil soluble initiator such as benzoyl peroxide. However, the weight ratio of the emulsifier to the monomer was approximately one to one and the microemulsion could not be diluted with water.
Canadian Patent Application No. 2,013,318, assigned to B. F. Goodrich is directed to a process for producing very fine-sized aqueous polymeric microemulsions. The process utilizes incremental addition of a monomer feed solution into an aqueous solution including one or more emulsifying agents and one or more water soluble or redox initiators. While this method may be used to produce such microemulsions, it is deficient in that the emulsion tends to discolor and that it is extremely difficult to obtain emulsions having a narrow particle size range profile. This reference suggests that the emulsions are suitable for use in paper production as a strength agent or an opacity improver. Other suggested uses include pigment binding, adhesives, binders for clay coatings, nonwoven saturations, textile coatings, beater addition polymers and binders for paint.
An article by Okuba et al, "Preparation of Asymmetric Polymer Film by Emulsion Blend Technique", Colloid & Polymer Science, 268:1113-1117 (1990), teaches blending two different particle size emulsions together to determine the tackiness properties of such blends. One of the starting emulsions disclosed is a poly(ethyl acrylate-methyl methacrylate) emulsion having a particle size of 0.02 microns. According to the article, this emulsion is prepared by combining the monomers in a glass flask with water, sodium sulfite, potassium persulfate and sodium dodecyl sulfate. The order or method of addition of the different reactants, initiators and emulsifiers is not specified.
European Published Patent Application No. 0 429 207, assigned to Rohm & Haas is directed to a method of treating or coating a substrate with an aqueous composition. The coating composition is an aqueous dispersion of copolymer particles having mutually incompatible phases and having an average particle size of about 20 to about 70 nanometers. The dispersion is prepared by emulsion polymerization techniques. In preferred embodiments, the particles are of a core/shell morphology where the core has a T.sub.g of at least 45.degree. C. and the shell has a T.sub.g of lower than 35.degree. C.
In commercial textile sizing operations, a sizing agent is applied to filament yarns to temporarily bind them together. This process inevitably involves applying an acidic material in a first pass to the yarns. Thereafter, the material is then neutralized by the addition of a base. This operation is both costly, as it requires the application of a multiple number of chemicals, and requires action to remove residual base.
Despite the above teachings, there still exists a need in the art for a textile size material derived from one or more ultrafine sized emulsions and which may be directly appled to textile fibers without requiring neutralization with base.